The present invention relates generally to the art of railway cars. More particularly, the invention pertains to a worm gear drive mechanism for gear operated railway car doors.
The invention is particularly applicable to rectangular metal doors of the type used on railway freight cars, and will be particularly described with reference thereto. However, it will be appreciated by those skilled in the art that the invention has broader applications and is adaptable to use with other types of doors and in other environments.
Rectangular metal doors of a known type used in railway cars include a generally rectangular frame typically comprised of top, bottom, and horizontal stiffeners, and opposed side members. Metal panels are secured to these frame members for completing the basic door construction. In most conventional railway cars, the frame members and metal panels are riveted and/or welded together.
Railway car doors are typically classified as either sliding doors or plug doors. Of the two, sliding doors are less complex, having a door configured to slide back and forth within a side panel of a railway car to selectively open and close an opening defined therein. Plug doors are more complex in that they are configured to first move laterally out of an opening defined in a railway car and then move longitudinally along a track disposed adjacent the railcar side panel.
Plug doors to be mounted on the side of a rail car include a series of panels or sheeting reinforced by horizontally disposed channels at the top, bottom and/or intermediate portions of the door. A pair of vertically oriented elongated support members such as pipes, rods or bars are configured to support the door on the railcar. The support members are typically provided with upper and lower cranks attached to the terminal end areas thereof which serve as lever arms for laterally moving the door into and out of the railcar door opening. Upon actuation of a driving mechanism, such as a manually operated gear assembly, the support members are rotated to cause corresponding rotation of the cranks. Rotation of the cranks, in turn, draws the door laterally outward from the opening until the door is supported on a track disposed adjacent to the side of the railcar. The door is movably supported on the track by roller hangers which enable the door to slide longitudinally along the side of the railcar.
One problem that occurs when the door is completely closed is that if a load falls against the inside wall of the door, an operating lever which controls movement of the door may spin and possibly move the door into an unwanted slightly or fully opened position.
A second problem occurs when the door is in the fully opened position. The support members have a tendency to rotate, thus causing the door to drift back into the side of the railcar. If this occurs, the ability of the door to slide longitudinally along the track may be inhibited. Furthermore, the door or the side of the railcar may become damaged because of the drifting action.
Another problem that occurs with existing railway car doors is found in a ratchet and pawl mechanism used for preventing movement of the door. That is, under certain conditions, the operating lever could still spin in spite of the pressure of a ratchet and pawl if the lever releases too fast and does not allow the pawl to engage the ratchet. This condition would occur if large forces were tending to push the door open and the operator released the lever while a rotational force was operating thereon and the pawl positioned on a peak of a ratchet tooth.
Accordingly, it has been considered desirable to develop an anti-spin/anti-drift worm drive arrangement for a gear operated door which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.
In accordance with the present invention, an anti-spin/anti-drift or stop mechanism is advantageously provided comprised of a worm drive for a gear operated planar door. The door is of the type having at least one elongated support member rotatably mounted thereto and which is selectively rotated through a drive mechanism by an operating mechanism to achieve door opening and closing. The operating mechanism includes an actuating member, such as a handle, lever or the like, which facilitates selective rotation of the at least one support member. An anti-spin/anti-drift mechanism operatively communicates with the operating mechanism to prevent undesired spinning of the operating mechanism which might otherwise allow the door to shift in an uncontrolled manner from one position to another.
According to another aspect of the invention, the anti-spin/anti-drift or stop mechanism includes a worm drive which is in continuous engagement with the drive mechanism.
According to yet another aspect of the invention, the worm drive includes a worm gear which operatively engages a spur gear for allowing selective rotation of the spur gear in a predetermined direction.
In accordance with a more limited aspect of the invention, the worm drive is mounted on a bearing plate of the door adjacent the drive mechanism.
According to a further aspect of the invention, the worm drive mechanism is advantageously provided to prevent either undesired spinning of the operating mechanism or drifting of the railcar door.
A principal advantage of the present invention resides in a provision of an anti-spin/anti-drift or stop arrangement which prevents an operating lever of a door from spinning if a load falls or is otherwise applied against an inside surface of the door.
Another advantage of the invention is found in an anti-spin/anti-drift or stop arrangement which does not impede or interfere with normal door operation.
Another advantage of the present invention resides in the provision of an anti-spin/anti-drift arrangement which prevents drifting of the door from a fully opened position.
Still another advantage of the invention resides in the continuous engagement of the anti-spin/anti-drift mechanism with the drive mechanism.
Yet another advantage of the invention is the provision of an anti-spin/anti-drift or stop arrangement which is relatively low in cost.
Yet another advantage of the invention is the provision of an anti-spin/anti-drift or stop arrangement which is easy to manufacture and retrofit to existing doors.
Still other benefits and advantages of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed specification.